Electric condenser



A ril 28, 1931. s. BOYER ELECTRIC CONDENSER Filed Dec. 4, 1925 Inventor sglves ter Boger, 105 W His Attornga Patented Apr. 28, 1931 UNITED STATES PATENT OFFICIE SYLVESTEB BUYER, OF LYN N, MASSACHUSETTS, ASSIG-NOR TO GENERAL ELECTRIC COM PANY, A CORPORATION OF NEW YORK .rmnc'rruc connnnsnn Application filed December 4, 1925. Serial No. 78,272.

My. invention relates to electric condensers, material for dielectric or insulation purposes and to the process of the manufacture of said material.

'5 It is common practice to make capacitors or condensers by separating the collecting elements with paper, which latter is sometimes saturated with some dielectric material such as pa'rafiine or transil oil. This paper, however, quite commonly has impurities in the form of conducting particles such as metal or carbon which often cause a condenser to break down; furthermore, paper thus treated has a comparatively low specific inductive capacity or permittivity.

It is an object of my invention to provide impregnated wood for dielectric or insulation purposes. It is an object to provide wood impregnated with such material as transil oil or with a material having high specific inductive capacity, such as nitro benzene, nitro-toluene, or acetonitrile or other similar materials which are fluid at ordinary temperature. It is also an object to provide a method of impregnating wood with any of the materials above mentioned. However, the invention will be more fully understood from the following specification and claims, reference being had to the accompanying drawing in which Figs. 1 and 2 show a form of condenser comprising the features of the invention.

In the manufacture of the material, the subject of the invention, the following process may be carried out. Any suitable wood, such as balsa wood, is first cut, seasoned, dried and vacuum treated to free it from volatile impurities. It is then impregnated with an insulating material such as transil oil or with a high resistance materialhaving high specific inductive capacity such as nitrobenzene, nitrotoluene, acetonitrile, or asphalt after which it may be compressed if desired to any desirable thickness; balsa wood for example may be readily compressed to one-half its thickness. The advantage of impregnating the wood before compressing it is that complete saturation of the wood 1s insured but the material may be used uncompressed. The wood, therefore, whether in its compressed or uncompressed condition, may be used as insulation or as a separator for the plates of a condenser. It will be understood that the high resistance material with which the balsa wood ,.or other wood is impregnated should preferably be free from impurities such as water or acids, to such an extent that its resistivity is of the order of 10 or over in ohms per centimeter cube. The process of preparing such materials is described in my copending application Serial No. 73,273, filed December 4, 1925, now Patent No. 1,769,874, dated July 1, 1930.

It is pointed out that materials such as nitro-benzene or nitro-toluene have an inductiv-ity of about 38 and that their resistivity may be raised to as high as 10 ohms per centimeter cube and over. Therefore, the capacity of the condenser may be greatly increased by substituting for paper impregmated with transil oil or wood impregnated with transil oil similar materials impregnated with nitro-benzene. It is also polnted out that the cost of balsa wood is less than that of paper and therefore a thicker dielectric may be used by substituting balsa wood for paper thus impregnated. Furthermore, by using a thicker dielectric the condenser can be run at a lower voltage stress per mil. Also by saturating balsa wood with materials of high specific inductive capacity and lower power factor I obtain an insulating material which may be used for radio panels and the like. I find that the specific inductive capacity of balsa wood saturated with nitrobenzene having hi h resistivity is in the neighborhood of 18 ut it depends somewhat upon the pressure applied when the wood is compressed. Of course the higher the saturation of the wood with the nitrobenzene the higher the specific inductive capacity. I find that red wood has a specific inductive capacity of about 7 and that when saturated with such a material as nitrobenzene it would give a dielectric of high specific inductive capacity and high resistivity.

When a wood is to be saturated with asphalt it is preferable that the temperature of the molten asphalt shall be in proximity of 175 degrees or 180 degreescentigrade.

thinner dielectric.

In Fig. 1 of the drawing a completed condenser in its casin made in accordance with the invention, is s own, In Fig. 2 the condenser is shown with the casing removed. The condenser shown in Fig. 1 is provided with terminals 41 and b which are connected with the plates of the condenser within the container 0 through the bushings e and f by means of leads 9 and it. As shown the lead 9 is connected with a number of metal strips 71 which connect with the metal elements of the condenser in the usual manner.- The lead it is connected toanoiher set of similar strips which are covered by an insulating plate j which latter prevents any short-circuiting between such terminals, and the frame. The protectin plate for the terminal z' is not shown or clearness ofillustration. The form of condenser shown in Fig. 2 is made in four sections all of which are clamped together by means of clamping plates is. After the sections are clamped together as indicated, they are placed within the container 0 which container is filled with nitro-benzene of the same. quality as that used for impregnating the wood. It will be understood that the condenser before it is filled is vacuum treated, the method being substantially the same as that, used in the manufacture of condensers immersed in oil.

It will be understood that while in the description of my invention therein I have, for the sake of clearness and in order to comply with the statutes, given concrete illustrations nevertheless I do not wish to be limited to the illustrations given, since the invention may be carried out by modifications and variations which will readily suggest themselves in view of the disclosure. Other kinds of wood may be substituted for the kinds of wood specifically mentioned, for examplecork may be used. Also the process described may be varied. The material may be impregnated with a dielectric after being compressed or other materials having high specific inductive capacity may be used in place of those mentioned, as for example p'araldehyde.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A condenser the collecting plates of which are separated by compressed wood, said wood being impregnated with a dielectric having high specific inductive capacity and resistivity, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

2. A condenser the collecting plates of tive capacity and high resistivity, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

3. A condenser the collecting plates of which are separated by compressed wood, said wood being impregnated with fluid dielectric having high specific inductive capac ity and high resistivity, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

4. A condenser the collecting plates of which are separated by compressed wood, said wood being impregnated with nitrobenzene.

5. A condenser the collecting plates of which are separated by compressed wood, said'wood being impregnated with nitrobenzene having a resistivity of 10 or over ohms per centimeter cube.

6. The process of preparing a dielectric which consists in impregnating wood with a fluid having high resistivity and compressing the wood.

7. The process of preparing a dielectric which consists in impregnating wood with nitrobenzene and compressing the wood.

8. A dielectric consisting of balsa wood impregnated with a dielectric having high specific inductive capacity and high resistivity, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

9. A dielectric consisting of balsa wood impregnated with a dielectric having high specific inductive capacity and high resistivity, said balsa wood being compressed, the inductivity being over 4: and the resistivity over 10 ohms per centimeter cube.

10. A dielectric consisting of wood impregnated with nitrobenzene having high specific inductive capacit and high resistivity, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

11. A dielectric consisting of wood inrpregnated with nitrobenzene having high specific inductive capacity and high resistivity, said wood being compressed, the specific inductive capacity being over 4 and the resistivity over 10 ohms per centimeter cube.

12. An electric condenser, the collecting plates of which are separated by compressed alsa wood saturated with nitro-benzene of a purity corresponding to a resistivity of 10 ohms per centimeter cube or over, the specific inductive capacity of the combined wood and nitro-benzene being of the order of 9 or over.

13. The process of preparing a dielectric which consists in taking balsa wood, drying and vacuum treating said wood, impregnatpurity corresponding to a resistivity of the order of 10 ohms per centimeter cube or over, and compressing the wood to substantially reduce its original bulk.

14. The process of preparing a dielectric which consists in taking balsa wood, drying and vacuum treating said wood, impregnatin the wood with nitro-benzene having a purity corresponding to aresistivity of the order of 10 ohms per centimeter cube or 'over, and compressing the wood until the pores of the wood are substantially saturated with the nitro-benzene.

- over 10 ohms per centimeter cube.

18. An electric condenser, the collecting plates of which are separated by compressed balsa wood saturated with nitrobenzene of a purity corresponding to a resistivity of 10 ohms per centimeter cube or over, the specific inductive capacity of the combined wood and nitrobenzene being of the order of '18 or over. i

In witness whereof, I have hereunto set my hand this thirtieth day of November,

1925. SYLV'ESTER BOYER. 

